Peter H. Raven served as director of the Missouri Botanical Garden from 1971 to 2010, when he was made president emeritus. During his time as director, he transformed the garden into the world’s leading tropical plant research facility and became known as a champion of plant conservation and biodiversity. He also held a post as professor of botany at Washington University, St. Louis, and co-wrote one of the leading textbooks in the field, Biology of Plants (7th ed. 2005). Here, Raven kindly agreed to answer a few questions posed by Britannica science editor Kara Rogers on plant biodiversity, from the impact of climate change to the significance of plant conservation.

Britannica: What do the current trends in climatic warming and human population growth mean for plant biodiversity?

Raven: The destruction of natural habitats that accompanies their conversion for other uses, the steady change that is occurring in world climates, and the destructive effects of invasive plants, animals, pests, and diseases have led us to estimate that about 20% of the world’s perhaps 350,000 species of land plants are in danger of extinction in nature over the short term (perhaps 10 years) and as many as half of the species by the end of the century.

Britannica: What biomes of the world are suffering the greatest declines in plant biodiversity?

Raven: Plant diversity is unevenly distributed around the globe. Very large numbers of unknown species are encountering massive growth in human populations, consumption, and the accompanying destructive activities in Southeast Asia. Islands in general, such as Madagascar and Hawaii, are areas where large numbers of species are disappearing. The Andean slopes of South America are another such area, as are the West Indies in general.

Britannica: How does the loss of plant biodiversity impact the ability of ecosystems to support other species?

Raven: Certain species, known as keystone species, are of particular importance, and when they are eliminated from ecosystems, the consequences may be serious for thousands of other species. Such species could be pines in forests where they are well represented, oaks, or other trees, or key species in grasslands. The loss of pollinators can also seriously affect the survival of flowering plants.

Britannica: Have certain areas of plant research been prioritized in order to facilitate plant conservation and preservation?

Without increased conservation and protection of the world’s plants, species such as this donkey orchid could go extinct in the coming decades. Credit: Gnangarra/CC Attribution 2.5

Raven: The development of techniques appropriate to the preservation of seeds at low temperatures in seed banks is particularly important, and a great deal of progress has been made recently. Calculating how to save plants and animals from the effects of a changing climate and learning about the properties of their communities and the ways in which they fit together in ecosystems now will provide suitable tools to facilitate our future efforts.

Britannica: How does the monetary valuation of plant-derived ecosystem services, in addition to aesthetic valuation, factor into plant and biodiversity conservation?

Raven: Plants are fundamental to all life on Earth, providing all of the food for all other organisms, directly or indirectly. For human beings, they provide innumerable medicines, and there are many more to be found. They store carbon and thus mitigate the effects of increasing carbon dioxide in the atmosphere, slowing global warming. Our dependency on plants is so complete that their value may be said to be beyond measure.